Project Summary Adolescent (ages 13-18) men who have sex with men (AMSM) experience a dramatic health disparity as they represent 2% of young people but account for almost 80% of HIV diagnoses. Despite this disproportionate burden, there is a conspicuous lack of evidence-based HIV prevention programs. Implementation issues are critical as traditional HIV prevention delivery channels (community organizations, schools, parents), have significant limitations when it comes to AMSM. eHealth interventions represent an excellent modality for delivering AMSM-specific intervention material where youth ?are.? We should not continue to deliver the same intervention when a participant is not responding. Rather, stepped-care strategies increase in intensity to meet the needs of those who do not respond to a less intense intervention. Using a Sequential Multiple Assignment Randomized Trial (SMART) design, we will evaluate the impact of a package of increasingly intensive interventions that have already shown evidence of efficacy with diverse adolescent and young adult MSM. The SMART design is an ideal approach to achieve the goals of this RFA because SMART designs mimic treatment decisions as they are made in real-world clinical settings. Collectively we brand our package of eHealth interventions as the SMART Program (Sexual Minority Adolescent Risk Taking). The Program package includes: (1) a universally-delivered, brief, online sexual health education program designed for sexual and gender minority youth regardless of whether they are sexually active (Queer Sex Ed); (2) a more intensive online intervention designed for diverse AMSM engaging in HIV transmission risk behaviors (Keep It Up!), and (3) the most intensive is a motivational interviewing (MI) intervention that will be delivered by MI therapists via online videochat (Young Men's Health Project). We will evaluate SMART Program impact and inform future implementation with three specific aims. Aim 1 is to test impact of the SMART Program and its constituent components on reducing HIV risk and increasing testing among. We will developmentally adapt existing content for AMSM using the ADAPT-ITT framework and linguistically adapt the SMART Program to Spanish speaking Latino AMSM. We will enroll a national sample of 1,878 diverse AMSM and test the efficacy of the Program using a SMART design. Aim 2 is to test if the SMART Program has differential efficacy across important sub-groups of AMSM based on race/ethnicity, urban/rural, age, socioeconomic status, and language. Aim 3 is to evaluate the delivery of the SMART Program nationally to inform its implementation and cost-effectiveness. To minimize the science-practice gap, we will utilize mixed methods to identify facilitators and barriers to the implementation of the SMART Program and its core components by collecting measures from the RE-AIM framework and performing cost analysis.